Table of contents

Rutherford backscattering spectrometry (RBS) and related techniques have long been used to determine the elemental depth profiles in films a few nanometres to a few microns thick. However, although obtaining spectra is very easy, solving the inverse problem of extracting the depth profiles from the spectra is not possible analytically except for special cases. It is because these special cases include important classes of samples, and because skilled analysts are adept at extracting useful qualitative information from the data, that ion beam analysis is still an important technique.

We have recently solved this inverse problem using the simulated annealing algorithm. We have implemented the solution in the `IBA DataFurnace' code, which has been developed into a very versatile and general new software tool that analysts can now use to rapidly extract quantitative accurate depth profiles from real samples on an industrial scale. We review the features, applicability and validation of this new code together with other approaches to handling IBA (ion beam analysis) data, with particular attention being given to determining both the absolute accuracy of the depth profiles and statistically accurate error estimates.

We include examples of analyses using RBS, non-Rutherford elastic scattering, elastic recoil detection and non-resonant nuclear reactions. High depth resolution and the use of multiple techniques simultaneously are both discussed. There is usually systematic ambiguity in IBA data and Butler's example of ambiguity (1990 Nucl. Instrum. Methods B 45 160–5) is reanalysed. Analyses are shown: of evaporated, sputtered, oxidized, ion implanted, ion beam mixed and annealed materials; of semiconductors, optical and magnetic multilayers, superconductors, tribological films and metals; and of oxides on Si, mixed metal silicides, boron nitride, GaN, SiC, mixed metal oxides, YBCO and polymers.

The microstructural variations of the Nd₆₀Al₁₀Fe₂₀Co₁₀ melt-spun ribbons and the as-cast rod were studied by high resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD) and differential scanning calorimetry. Nano-clusters in glassy matrix in both melt-spun ribbon and the as-cast rod samples were observed by HRTEM, though no obvious crystalline reflections were displayed in either the XRD or selected area electron diffraction patterns. The magnetic properties of the rod sample were compared to that of the ribbons. It was found that the coercivity of the alloy increases with the size of the nano-scaled clusters, while the cluster size increases with the reduction of cooling rate at which the sample were prepared. The relationship between the microstructure and magnetic and thermal properties of the Nd based alloy were discussed by random anisotropy model.

We report on Fe films grown on Au-buffered Si(001) showing perpendicular magnetization at ambient temperatures. The in-plane magnetization in ultra-thin Fe films grown at 150 K reorients irreversibly out-of-plane as a result of annealing close to room temperature. A Au cap layer which is expected to segregate to the top of the Fe film may be responsible for this behaviour. This hypothesis is based on the observation of an in-plane to out-of-plane reorientation of magnetization upon the growth of an ultra-thin Au cap layer on a slightly thicker Fe film. The origin of such a strong out-of-plane anisotropy of Fe induced by Au is discussed.

The classical Preisach model (PM) of magnetic hysteresis requires that any minor differential permeability curve lies under minor curves with larger field amplitude. Measurements of ferromagnetic materials show that very often this is not true. By applying the classical PM formalism to measured minor curves one can discover that it leads to an oval-shaped region on each half of the Preisach plane where the calculations produce negative values in the Preisach function. Introducing an effective field, which differs from the applied one by a mean-field term proportional to the magnetization, usually solves this problem. Complex techniques exist to estimate the minimum necessary proportionality constant (the moving parameter). In this paper we propose a simpler way to estimate the mean-field effects for use in nondestructive testing, which is based on experience from the measurements of industrial steels. A new parameter (parameter of shift) is introduced, which monitors the mean-field effects. The relation between the shift parameter and the moving one was studied for a number of steels. From preliminary experiments no correlation was found between the shift parameter and the classical magnetic ones such as the coercive field, maximum differential permeability and remanent magnetization.

Magnetic tunnel junctions (MTJ) with non-collinear anisotropy axes of magnetic layers have been fabricated for reading head and sensor applications. It is shown that crossed anisotropies of magnetic layers improve sensor sensitivity and time-response compared to the conventional case of aligned anisotropies. The developed micromagnetic model is in good agreement with magnetoresistive properties of fabricated junctions.

High-energy milling process has been used to prepare Al₇₂Cu₁₇Fe₁₁ and Al₈₀Cu₁₀Fe₁₀ alloys. X-ray diffraction (XRD) and Mössbauer experiments were used to investigate the structural properties of the milled and annealed samples. Both alloys were milled for up to 150 h and Mössbauer spectroscopy shows that the milled Al₇₂Cu₁₇Fe₁₁ alloy has no free α-Fe phase, while the milled Al₈₀Cu₁₀Fe₁₀ has 12% of α-Fe. XRD patterns indicate both compositions are disordered nanostructured phases. Differential scanning calorimetry measurements were performed to study structural phase transitions in the milled samples. The 150 h milled samples submitted to annealing process revealed that the alloys have distinct Fe environments, which seeds the formation of different crystalline phases. In the Al₈₀Cu₁₀Fe₁₀ case, the annealing process leads to the formation of Al₇Cu₂Fe and Al₁₃Fe₄ phases, imbedded in an α-Al matrix, at 923 K. The measured hyperfine parameter values of the Al₇Cu₂Fe phase are δ = 0.14 mm s⁻¹ and Δ = 0.17 mm s⁻¹. For the Al₂₃CuFe₄ phase observed in the annealing temperatures up to 873 K, these are the parameter values δ = 0.25 mm s⁻¹ and Δ = 0.28 mm s⁻¹. For the Al₇₂Cu₁₇Fe₁₁ case, the annealing process produces chemically disordered crystalline Al₇Cu₂Fe. The latter phase is stable at temperatures up to 923 K and it has isomer shift and average quadrupole splitting values of 0.19 mm s⁻¹ and 0.39 mm s⁻¹, respectively.

Coupled mechanical and electronic behaviours of single walled open carbon nanotubes (CNTs) under applied electric field and tensile loading are investigated by the use of quantum mechanics as well as quantum-molecular dynamics techniques based on the Roothaan–Hall equations and the Newton motion laws. Different failure mechanisms and mechanical properties are found for CNTs subjected to electric fields and that subjected to tensile load. The electric field induced breaking in CNT begins from the outmost carbon atomic layers while the tensile load breaks the nanotube near its middle at 300 K. Electronic polarization and mechanical deformation induced by an electric field can significantly change the electronic properties of a CNT. Under electric field, the CNT can be stretched but the toughness is much lower than that under mechanical loading. Applied tensile loading causes no electronic polarization even in a metallic tube but it indeed changes the energy gap of the tube, thus exhibits influence on field-emission properties of CNTs. When a tube is tensioned in an electric field, the critical tensile strength of the tube may decrease significantly with increasing intensity of electric field. The coupling of mechanical and electrical behaviours is an important characteristic of CNTs.

Er³⁺ doped Na₂O–Nb₂O₅–TeO₂ (NNT) glasses suitable for making optical waveguide devices has been fabricated and characterized. Intense 1.53 μm infrared fluorescence and green upconversion luminescence were observed under 975 nm diode laser and 798 nm laser excitation. The optical absorption, the Judd–Ofelt parameters and the spontaneous transition probabilities have been measured and calculated. The quantum efficiency of 1.53 μm emission band is proved to be ∼100%. The maximum emission cross-section is 1.02×10⁻²⁰ cm² at 1.533 μm, and it is more than 30% higher than the values in silicate and phosphate glasses. Under 798 nm excitation, strong green and weak red upconversion luminescence was observed at room temperature. The 546 nm green band shows a broad full-width at half-maximum of 16 nm. Intense and broad green upconversion fluorescence in Er³⁺ doped NNT glass can be used in colour display, undersea communication and infrared sensor. High concentration of Na₂O is a benefit to developing waveguide device from the glass.

We study the alignment of the lattice structure of single walled carbon-nanotubes (SWNT) produced on a highly oriented pyrolytic graphite (HOPG) surface using controlled growth in ultrahigh vacuum (UHV). With scanning tunnelling microscopy (STM) at low temperature (T = 77 K) the HOPG and the SWNT were imaged in UHV simultaneously with atomic resolution. The lattice structure of the SWNT was compared to the HOPG. For this purpose we present a technique for evaluating the mutual orientation which uses the measured lattice vectors of the HOPG surface as a reference for distortion and drift effects in the STM image. The quantitative evaluation showed an alignment of the SWNT lattice structure to the structure of the substrate.

Recent simulations by So et al (2002 J. Phys. D 35 2978–87) have shown inter alia that in CF₄ where there are two negative ions of comparable density, the plasma is structured, in that there are essentially three regions so far as the negative ions are concerned. In the inner region one negative ion species is concentrated, in the outer region electrons dominate over negative ions, while the intermediate has only one species of negative ion.

This confirms earlier work (Franklin R N 2002a J. Phys. D: Appl. Phys.35 536–42; 2002b J. Phys. D: Appl. Phys. 35 747–50) and justifies extending that work to cover situations where there is a multiplicity of both positive and negative ions.

In this paper we give explicit results for the central electronegativities and electropositivities for the case of two species of ion of each sign, and also determine the relative sizes of the regions occupied by the negative ions. By effectively varying the electron temperature through the ionization rate, we indicate how these quantities vary with gas pressure.

As an appendix we generalize to the case of `j' positive ions and `k' negative ions.

In this paper we examine critically when the term diffusion is an appropriate description of the transport processes occurring in steady state active plasmas. It is suggested that ambipolar flow is a more correct and general expression. The paper examines in detail the situations in: (a) conventional active low temperature electropositive plasmas generated by electron impact such as the positive column of a d.c. gas discharge; (b) such plasmas where the electrons are magnetized and the ions not; (c) electronegative plasmas such as those used in plasma processing where there is separation into an ion–ion core and an outer electron–ion plasma.

A narrow capillary plasma channel, with a sizeable depletion of the electron density on the channel axis, has been proposed to guide a laser pulse over a length of several to several tens of centimetres. We discuss the possibility to significantly improve the wave-guiding properties of such a channel by applying an axial magnetic field. Our analytical and numerical studies show that a pulsed axial magnetic field of 10 T in a hydrogen capillary plasma at a pressure of 50 Torr will reduce the on-axis plasma density by a factor of three, and the full width at half maximum of the density profile by a factor of two. The resulting parabolic plasma density profile is expected to be more efficient in guiding laser pulses.

The usage of low-cost silicon-based solar cells is limited by their tendency to degrade on prolonged exposure to sunlight. Current research has indicated that the inclusion of nano-particles in the plasma-deposited film enhances its efficiency considerably. It is therefore essential to identify the plasma operating conditions such that nano-particles are formed and deposited in the film. The early stages of cluster formation, nucleation and coagulation are still open to experimental and theoretical investigation. In this paper, a simulation of the first stage of particle formation in capacitively coupled radio-frequency discharges in SiH₄ is attempted. A molecular dynamics based model has been set up to simulate one of the principal reaction pathways in cluster formation. This simulation model appears to produce valid and meaningful trends. Further studies are planned to explore the effect of other parameters and alternate pathways.

A novel procedure using plasma sputtering in an electron-cyclotron-resonance device has been applied to clean archeological MOCHE artefacts, unearthed at the Royal Tombs of Sipán. After successful cleaning, the pieces were analysed by a variety of complementary techniques, namely proton-induced x-ray emission, Rutherford backscattering spectroscopy, x-ray diffraction, electron microscopy, and inductively coupled plasma mass spectroscopy. With these techniques, it has been possible to not only determine the profiles of the gold and silver surface layers, but also to detect elements that may be relevant to explain the gilding techniques skillfully developed by the metal smiths of the MOCHE culture.

The subject of this paper is the modelling of d.c. and a.c. high-intensity Hg-discharge lamps with differently shaped electrodes. Different arc attachments on the electrodes are studied and insight for the development of new electrodes is gained. The model includes the entire discharge plasma (plasma column, hot plasma spots in front of electrodes, near-electrode non-LTE-plasma) as well as anode and cathode. No subdivision of the discharge space into different regions is necessary (like space charge layer, ionization zone, plasma column). This is achieved by using a differential equation for a non-LTE electrical conductivity which is applicable for local thermal equilibrium (LTE-)regions as well as for non-LTE plasma regions close to the electrodes in a high pressure plasma. Modelling results for a 0.6 MPa mercury discharge considering six different electrode shapes (anode and cathode) are presented and compared with experimental results. The electrodes have different diameters and different electrode tips, such as hemispherical, flat, or conical tip with 60° or 90° apex angle. Furthermore, an electrode with a larger diameter in the mid section of the rod is investigated.

An investigation is made of the threshold for microwave breakdown in air in situations where the microwave power is strongly modulated or stochastically varying in time as, e.g. in communication systems based on multi-carrier operation where interference between the carriers may cause occasional high power peaks in the microwave power. Thresholds are established for the scenario of coherent and co-phased carriers as well as for breakdown in an electric field with a stochastically varying amplitude.

The results of spectroscopic studies of plasmas generated in dielectric barrier discharges between flat ceramic electrodes supplied by AC voltage in pure hydrogen atmosphere under low-pressure conditions are presented. Stark splitting of the H_α Balmer line was used to measure the electric field strengths in the discharge volume. The optical instrumentation and the detection system allow to perform spatial and time resolved measurements separately for the π and σ Stark components. The measured spatial light intensity distributions are averaged data obtained by integrating signals from many half-periods of the AC voltage supply. This fact has been taken into account when comparing our averaged data with results of theoretical models which are yielding time dependent results.

Characteristics of crystalline structure, roughness and nanotribology of ZnO thin films deposited under various power conditions were achieved by means of x-ray diffraction and scanning probe microscopy (SPM). The ZnO thin films were deposited on the silicon (100) substrates by a radio frequency magnetron sputtering system. Fractal analysis was derived from SPM images, to calculate the fractal dimension complexity of the surface geometry, via a substituting structure function. The results show that the roughness decreases and nanowear rate increases as the sputtering power increases. In addition, the fractal dimensions of the ZnO thin films are also presented.

Using nanoindentation, we investigate hardening mechanisms in steered arc (SA) evaporated and electron-beam (EB) evaporated molybdenum thin films. Both films have columnar grains, with the column diameters ranging between 22 and 170 nm in the SA films and 30 and 40 nm in the EB films. The Hall–Petch relation is extended out to hardness values between 6 and 12 GPa. Analysis of nanoindentation creep data (creep, load relaxation, and rate change) reveals that, in the SA films, thermally activated glide is rate controlling, and that grain size has little effect on the underlying rate processes even down to 22 nm. There is evidence based on x-ray diffraction (and supported by the literature) that the EB films contain high densities of interstitial loops resulting from argon ion bombardment during deposition. The analysed creep data indicate that these loops affect the thermal activation of dislocations.

Among perovskite oxides strontium titanate (STO) SrTiO₃ undergoes a metal–insulator transition at very low carrier concentration and exhibits high mobility values at low temperature. We exploited such electrical properties and the structural compatibility of perovskite oxide materials in realizing ferroelectric field effect epitaxial heterostructures. By pulsed laser deposition, we grew patterned field effect devices, consisting of lanthanum doped STO and Pb(Zr,Ti)O₃. Such devices showed a resistance modulation up to 20%, consistent with geometrical parameters and carrier concentration of the semiconducting channel.

Stacked SiO_xN_y/Ta₂O₅ films have been deposited on strained-Si_0.82Ge_0.18 layers at a low temperature in a microwave plasma using NO and tantalum pentaethoxide. The chemical binding states and composition of stacked Ta₂O₅/SiO_xN_y/SiGe films have been studied by time of flight secondary ion mass spectroscopy and x-ray photoelectron spectroscopy. Effects of annealing on the electrical properties of the dielectric films have been studied using high frequency capacitance–voltage, current–voltage and conductance–voltage techniques.

The influence of titanium content and heat treatment temperature on the optical and mechanical properties of TiO₂/γ-glycidoxypropyltrimethoxysilane and methyltrimethoxysilane hybrid films processed by the sol–gel technique are studied for photonic applications. Waveguide film with a thickness more than 1.60 μm is prepared by a single spin-coating process and low temperature heat treatment. Thermal gravimetric analysis, UV–visible spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy are used to investigate the optical and structural properties of the hybrid organic–inorganic films. The results indicate that a dense, low absorption, and high transparency in the visible and near infrared range waveguide films can be obtained at a low temperature. The hardness and Young's modulus of the films are characterized by a nanoindenter and they show a dependence on the heat-treatment temperature. Hardness as high as 6.60 Gpa is obtained in 0.5 M titanium content film and heat-treated at 800°C. It is proposed that the high hardness of the film may be related to the carbon and titanium content in the film.

The phase matrix of irregularly shaped randomly oriented large fractal particles is studied in the framework of the ray tracing approach for various refractive indices. The fractal particle model can be used for modelling local optical characteristics of various natural light scattering media with irregular particles, including oceanic water, crystalline clouds and solid aerosols. For nonabsorbing large particles the theory does not contain any fitting parameters except the refractive index of particles, which is either known (ice clouds) or has generally unknown distribution in a local volume of a scattering medium (dust aerosols and oceanic suspensions).

The principle of differential algebra is applied to analyse and calculate arbitrary order curvilinear-axis combined geometric–chromatic aberrations of electron optical systems. Expressions of differential algebraic form of high order combined aberrations are obtained and arbitrary order combined aberrations can be calculated numerically. As an example, a typical wide electron beam focusing system with curved optical axes named magnetic immersion lens has been studied. All the second-order and third-order combined geometric–chromatic aberrations of the lens have been calculated, and the patterns of the corresponding geometric aberrations and combined aberrations have been given as well.

Current numerical simulations of laser materials processing are usually based on a greatly simplified process model in order to allow for short computation times. This significantly decreases their flexibility and ability for simulation of the great variation of today's processes and, consequently, accounting for their subtle but important differences. The theory utilized for building a simulation tool presented in this paper can be said to be truly three-dimensional as opposed to other reported work that uses symmetric boundary conditions. The interaction of the free surface of the liquid face is modelled which provides a significant increase in the amount of process detail captured. The investigators contend that numerical modelling of the above can only be achieved credibly using high performance computing methods, in particular parallelization techniques.

In this paper, the frictional behaviours of single and multi-balls slid against micro-grooved silicon surfaces were investigated by using a micro-tribotester built inside a scanning electron microscope. Various micro-grooves were fabricated on the silicon surface to investigate the frictional behaviour with respect to the contact geometry between the surface asperities. Particularly, fast Fourier transform (FFT) analyses of the friction signals were performed with the motivation to assess the contact conditions. The primary objective of this paper was to understand better the asperity interaction condition at the sliding interface by analysing the frictional force signal using FFT.

The experimental and numerical simulation results showed that the relative geometric ratio and the distribution of contact asperities on the surfaces could be predicted by the power and frequency spectra of the FFT analysis of the friction signal. Also, the frictional behaviour for multi-asperities was found to be the result of superposition of the frictional interaction of each asperity contact. It is expected that these observations will be utilized for the design of micro-structured surface with optimum geometry for better tribological performance.